Elements such as arsenic, antimony and selenium are widely used as industrial materials for semiconductor and the like. However, impacts of these elements on organisms are concerned when these elements leak out into the environment, since the elements can be toxic to the organisms.
Conventionally, as a method for removing these elements, a method including adding a flocculant such as poly aluminium chloride (PAC) to wastewater containing harmful inorganic arsenic such as arsenious acid to allow the arsenic to be agglutinated and adsorbed on the flocculant and iron in the raw water, and removing a precipitate by filtration after allowing the arsenic to precipitate, a method including adsorbing an arsenic compound and the like by an activated alumina or a cerium type adsorbent, and the like are commonly known.
Recently, the inventor of the present invention has proposed a method for making a harmful arsenic compound, antimony compound and selenium compound harmless by alkylating these compound using an organic cobalt complex (a vitamin B12-type compound) (e.g., see patent literatures 1 and 2). According to these methods, the harmful arsenic compound, antimony compound and selenium compound are allowed to be harmless in an easy and simple manner with a high efficiency.